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package mediacleaner;

/**
 *
 * @author m.rogers
 */
import java.util.*;
import java.io.*;

/**
 * Recursive file listing under a specified directory.
 *
 * @author javapractices.com
 * @author Alex Wong
 * @author anonymous user
 */
public final class FileListing
{

    /**
     * Demonstrate use.
     *
     * @param aArgs - <tt>aArgs[0]</tt> is the full name of an existing
     * directory that can be read.
     */
    public static void main(String[] aArgs) throws FileNotFoundException
    {
        File startingDirectory = new File(aArgs[0]);
        List<File> files = FileListing.getFileListing(startingDirectory);

        //print out all file names, in the the order of File.compareTo()
        for (File file : files)
        {
            System.out.println(file);
        }
    }

    /**
     * Recursively walk a directory tree and return a List of all
     * Files found; the List is sorted using File.compareTo().
     *
     * @param aStartingDir is a valid directory, which can be read.
     */
    static public List<File> getFileListing(File aStartingDir) throws FileNotFoundException
    {
        validateDirectory(aStartingDir);
        List<File> result = getFileListingNoSort(aStartingDir);
        Collections.sort(result);
        return result;
    }

    // PRIVATE //
    static private List<File> getFileListingNoSort(File aStartingDir) throws FileNotFoundException
    {
        List<File> result = new ArrayList<File>();
        File[] filesAndDirs = aStartingDir.listFiles();
        List<File> filesDirs = Arrays.asList(filesAndDirs);
        for (File file : filesDirs)
        {
            result.add(file); //always add, even if directory
            if (!file.isFile())
            {
                //must be a directory
                //recursive call!
                List<File> deeperList = getFileListingNoSort(file);
                result.addAll(deeperList);
            }
        }
        return result;
    }

    /**
     * Directory is valid if it exists, does not represent a file, and can be read.
     */
    static private void validateDirectory(File aDirectory) throws FileNotFoundException
    {
        if (aDirectory == null)
        {
            throw new IllegalArgumentException("Directory should not be null.");
        }
        if (!aDirectory.exists())
        {
            throw new FileNotFoundException("Directory does not exist: " + aDirectory);
        }
        if (!aDirectory.isDirectory())
        {
            throw new IllegalArgumentException("Is not a directory: " + aDirectory);
        }
        if (!aDirectory.canRead())
        {
            throw new IllegalArgumentException("Directory cannot be read: " + aDirectory);
        }
    }
}
